Sealing joints and other leak locations in pipelines has always been a critical concern, and has become more important as efforts have increased to protect the environment. Liquid chemicals, sewage, toxic gases, and other fluid-like materials such as fine dust must be conducted through pipelines without leakage of the material from the pipeline and without contamination from outside. To seal joints, pipeline installers typically encircle the joint with a cylindrical coupling consisting of either two semi-cylindrical pieces fastened together to clamp down on the pipe ends, or a single cylindrical piece having an axial slit which allows the coupling to be opened by an amount sufficient to fit over the pipe ends.
Annular gasket members, such as O-rings, may be placed around the pipe ends beneath the coupling to block the escape of fluid axially between the coupling and the pipe ends, but it is then necessary to block escape of fluid outwardly through the axial slit of the coupling. Several prior devices for this purpose have been developed, as described in U.S. Pat. Nos. 4,360,227; 1,607,943; 2,913,262; 3,153,550; 4,664,428, and 5,086,809.
U.S. Pat. No. 4,664,428, which is incorporated herein by reference in its entirety, describes a sealing plate spanning the axial slit of a coupling and contacting two O-rings positioned on opposite sides of the joint in the pipeline. The sealing plate is positioned outside the O-rings between them and the coupling and has axial gaskets along edges of the sealing plate for preventing passage of fluid from between the O-rings to the outer surface of the sealing plate. This sealing plate has the disadvantage, however, that it can only be used with continuous annular O-rings which must be properly positioned on the pipe ends before positioning the sealing plate over the O-rings and then positioning the coupling over the sealing plate and O-rings. Couplings having arcuate gasket members attached to the inside of the coupling cannot be used with such a sealing plate. During the positioning and tightening of the coupling, the O-rings may become misaligned or the sealing plate may become misaligned with respect to the O-rings. These problems in installation can be particularly difficult when couplings are being placed under water by divers, in confined areas, in open trenches or channels containing flowing water, or on existing pipelines to repair a joint or leak.
Thus, there is a need in the art for a sealing plate that can be installed reliably and conveniently in awkward situations, and that can be used with couplings which have O-ring sections attached to the interior of the couplings.